N-carboanhydrides



Patented July 17, 1951 PATENT OFFICE-I 2,560,584 n-cmonumaro'nsi Robert Neal MacDonald, N'ew Castlc,-,Del'.,- as

sign'or to; ELI. du Pontde Nemoursr' and Com pany, Wilmington, Del-., va corporation oi Dela'--' ware No Drawing.. Application February-2,1949; Serial N0. 74,241

18Glaim sr (claw-30 1 r This invention relates to new types of polyamides and the intermediates therefor, and more particularly to N-carboanhydrides of alphaamino acids of unusual ring structure and the polymers derived therefrom. 5

This application is a continuation in part of my copending applications Serial No; 76621581 filed August 5, 1947, nowaba'ndoned', and Serial N0. 778,458; filed October 7, 1947.

This invention has as an object the repare-- tion of new organic compounds.- A" further ob ject is the preparation of new intermediates fer: condensation polymers; Another object is" the preparation of new polymers, including. ccpoly mers;

These objects areaccomplished bythe renew ing invention of N'carboanhydrides of" alpha amino" acids Wl er'einthe carbon between the" amino nitrogen and the aeyl carbon- ,aspire" carbon, i. e., the carbon form's the one com'rnom member of two rings-one being the N-carboanhydride ring. These N-carboanhydrides' may" be" prepared the reaction of the alpha-amino'acid' having the alpha carbon a member of a ring. with: ethyl; 5

chloroformat'e, thenreacting the carboethoxy derivative with thionyl chloride to form the corresponding acid chloride whichsplits out) ethyl chloride to yield the desiredproduct'. However, the route through the carbobenzyloxy derivative is preferred because of greater ease of handling and greater reaction efiiciencyr They may also be prepared by reacting the amino acid salt with phosgene.

The invention is illustrated by the? following.-

examples but the invention i'sn'otlimited totfiese particular modifications;

EXAMPLE. 1

0'1 5;5 tetrametliylenespirofiu damme- A; Preparation is prepared, by the methodofI-Ienz'e amiss-ear, J'. Am. Chem. Soc '64 522-3 (1'942)"-as"folloWs -:I

In a five-liter, round -b'ottomed three ne'cl iedf;

flask equipped with a reflux-condenser anther mometer, a' mechanical stirrer and a, dropping; funnel, a mixture of"260".4 g.' (3111 moles-)1 ofc c1opentanone,, 684- g.v (6' moles) of. ammonium Other objects will appear'hereina'fterf 15 2 alcohol, and soc mlsl of water are he'ated' te 54 C'LimaL-water bath'. As the-substanceis vigorously agitated and heated at 54'-60 (3., a solution of:

mlstof: water is added dropwise ove'r a period ofone liou'ra Stirringis: continued at -57- 60: C; for three hours, and the temperature is then raised to C fori'15 minutes to destroy." any excess; ammonium: carbonate The reaction mixture is then transferred to a f'our -liter beaker and concentra-tedion a steam bath to aboutithree fourths its-volume; Upon cooling, a snow= white precipi tate separates out which is' filtered, washed withvwater, then with alcohol, and air dried. There is' -thus'-. obtained 2851s. of 5,5-tetramethylenespirohydantoin: melting; at: 204-206 0'. (com-- pared to1204 -205 C. as given in the referenceabcve); Onconcentrating the motherliquor and cooling in ice; thereis. obtained an additional-- 56 gt;ofi'product melting at-205e-206" C. The total yieldzof relatively'pure hydantoin: is 34:1 g.-(74% of-I'theory), on re'cr-ystallization from 1800'mlsr of boiling; absolute alcohol; there is obtained: 258A: g. (56%: of theory) of glistening. white:

Bi- Preparationof 1-ammocyclopentanecarbom charcoal; and the solution. neutralized with a slight excess of ammonium hydroxide to I give asnow white. crystalline precipitate of l-amino.--

The product is cyclopentanecarboxyl'ic acid."

Washed with 65 mls. of water in portions, after which only a very faint sulfate test is given by the wash water. After being dried for two days at 65 C., the product weighs 75.6 g. (46% of theory) ANALYSIS Calculated for orrnoi'Nz c, 55.79%; H, 8.59%; N, 10.85%; neutral equivalent (N. E.), 129.16

Found C, 55.90%; H, 8.59%; N, 10.72%; N. 131., 128.4 C, 55.57%; H, 8.67%; N, 10.69%; N. E., 128.0

1-aminocyclopentanecarboxylic acid may also be prepared by the method of Zelinsky et al.,

J. Russ. Phys. Chem. Soc., 43 1097.

C. N-carboanhydrz'de of l-aminoc'yclopentanecarboxylic acid I In a 500 m1. round-bottomed, four-necked flask equipped with a thermometer, a phosgene inlet tube, a mechanical stirrer, and a condenser open to. the atmosphere only through a drying tube, a slurry of 25.8 .g. (0.2 mole) of l-aminocyclopentanecarboxylic acid in 250 mls. of purified, dry dioxane is stirred vigorously at 90 C. as phosgene is passed in for 30 minutes at a rate of 0.01 mole per minute [representing 0.3 mole total, 50% excess over theory]. The system is stirred at 90 C. for an additional 30 minutes and then pressure filtered under anhydrous conditions with nitrogen through a sintered glass funnel into a distilling flask. There is thus obtained on the filter 15.8 grams (47.5% recovery based on the amino acid) of 1-aminocyclopentanecarboxylic acid hydrochloride.

' The filtrate is concentrated in the distilling flask under reduced pressure of the water pump at 55 C. until the volume is reduced to about 50 mls., whereupon it is transferred to an Erlenmeyer flask and 400 mls. of petroleum ether added; The oil that separates out crystallizes rapidly upon cooling. The precipitate is filtered and rinsed with petroleum ether in a nitrogen dry box (i. e., in a closed space under anhydrous conditions and also under a positive pressure of nitrogen) to give 14.4 g. (89% of theory) of. slightly colored crystalline product. This material is treated with decolorizing charcoal in 140 ml'sjof warm benzene, filtered hot, and 100 mls. of warm petroleum ether added. A voluminous, white precipitate is formed which is removed by filtration and then recrystallized from 100 mls. of warm benzene. There is thus obtained 9.9 g. (60% ortheory) of the N-carboanhydride of 1- aminocyclopentanecarboxylic acid as snow white, tiny needles melting at 128 C.

ANALYSIS Calculated for C'1H903N: C, 54.19%; H. 5.85%; *N,--9.03, Found: C',-.,54.l7%; H, 5.86%; N, 9.08%

EXAMPLE II A. Preparation of 5,5-pentamethylenespirohydantoin =o Nnmoo. NaCN .H2O Y This preparation is carried out in general 'by the method of Bucherer and Lieb, J. praktChem.

[2], 141 5 (1934), and is described under Example I, Part A, except that 308.7 g. (3.15 moles) of redistilled cyclohexanone are used and the heating time at 90 C. is one-half hour. After cooling the reaction mixture, the resulting precipitate is filtered and Washed with three liters of ice-cold distilled water. There is thus obtained 330 grams (60% of theory) of 5,5-pentamethylenespirohydantoin as snow white, glistening crystals melting sharply at 216 C.

- ANALYSIS Calculated for CsHuOzNz: C, 57.13%; H, 7.14%;

--Found:

C, 57.23%; H, 7.27%; N, 16.50% C, 57.25%; H, 7.04%; N, 16.31%

B. Preparation of 1-aminocyclohemanecarboxylic NH H2504 20 --v This preparation is carried out in general in the .same fashion as described previously in Exmoved by filtration, washed with 2 liters of distilled water and finally dried in a vacuum desiccator. There is thus obtained g. (66% of theory) of l-aminocyclohexane carboxylic acid as glistening, snow white crystals.

ANALYSIS Calculated for CvHnOzN! N. E., 143.2 Found: N. E., 143.8 and 143.9

0. Preparation of N-carbobenzyZoxy-I-aminocyclohemanecarbomylic acid I coon 05115011200 001 s HCl NHCOOCHzCuHs In a one-liter, three-necked flask equipped with a, stirrer and two dropping funnels are placed 71.6 g. (0.5 mole) of 1-aminocyclohexanecarboxylic acid and 245 mls. (0.5 mole) of 2.038 N sodium hydroxide. While cooling this solution in an ice bath and continuously stirring it, 107.7 g. (0.5 mole) of carbobenzyloxychloride and 122.7 mls. (0.5 mole) of 4.076 N sodium hydroxide are added simultaneously from the two dropping funnels over a period of one hour. The acid chloride addition is started slightly ahead of that of the sodium hydroxide, the rates being adjusted so that the addition of both ends together. Stirring at ice-bath temperature is continued for two h0urs,,after which the reaction mixture is filtered and the filtrate extracted four times with ether. While kept at 0 C. by external cooling, the solution is neutralized with 49 mls. of concentrated hydrochloric acid, whereupon a white precipitate forms. It is separated by filtration, washed with cold distilled Water until free from chloride ion,

and dried over calcium chloride in a vacuum axe -ascdesiccat'or. N-carbobenzyloxy-lraminocyclohexs anecarboxyli'c acid, melting at 15418-156 (I, is.

thus obtained, 7217 g. or 52% oftheory.

ANALYSIS Calculatedfor Cal-119N05 N-z 277.3 Found N. E., 275.4, 276A D. Preparation of the 'N-carhoanhydride. 1 aminocyclohexanecarbomylic acid Fifty g: (0.181 mole) of N-carbobenzyloxys-l aminocyclohexanecarboxylic' acid. is mixed at room temperature with 119 g. (one mole) of thionyl chloride in a 200 ml: distilling-flask protected; with; tubes; containing; a, drier. Evolutionof? sulfur dioxide and hydrogen-.chloridebegins with-, in; one; minute, and. solution is' complete; within; ten; minutes; The! reaction; mixture; is allowed, tozstandzovernight, after which it. is still. a clear; amber: color; Theexcess thionyl chlorideais I181? moved underv reduced pressure. leaving: a. solid product... Thiscrudematerial is-washed with petroleumiether in. aBiichner. funnel: under: anhy" drous conditions;.27 g. (88.5%. of theory), of. the; N-carboanhydride. of l-aminocyclohexanecars boxylic. acid being thus; obtained. If a: purer..." produchis: desired, itmay be taken; up in 60. mls; of: boiling methylene. chloride, treated with: deoolorizing charcoal at the boil, filtered hot, 50';

m1s..of petroleumether. added,v and the. resulting;

solution cooled at-Dry-Ice temperature overnight; The; crystalline product. is. then filtered off, washed first'with a; mixture of four parts. DES-=- troleum: etherto onegpart. methylene chloride-my:

volume, and washed finally with petroleum-ether."

alone. After drying, 17.1 g. (56% of theory) of snow white, crystals melting sharply at 114t8 115.2? C; iseobtained.

ANALYSIS Calculatedfor GaHuNOs: C, 56.79%; H, 6.55%;

N,.8.28.%. Found: C, 57.09%; H,.6.66%; N, 8.20%.

I-aminocycloheatanecarboalylic' acid N-carboanhydrid'eas ia blowin'g agent for spongerubber Fifty (50) parts of pale creperubber (Williams; plasticity index. No. 90) is. thoroughly, broken. down by millingfor 20 minutes on a rubber mill" at. roomv temperature. zinc oxide, 2.5 parts of stearic acid, 25'parts off. Camel Whiting (calcium carbonate filler), 1.7" partsv of I sulfur, 0.75 part of rubber. accelerator. (91%, zinc. salt of mercaptobenzothiazole andj9% N,N'-di(o-toly1)' guanidine) and 5L0 parts offf Circo Oil (light processing mineral'oil) is .mill'ed.

ed into the plastic mass, the'well-milledmaterial! is sheeted out at,a thickness of166 mils, a two,- inch. disk is cut fromthesheet, placedxina circular confined space. /2 thick, heatediat 150 CI;

for 20 minutes. Upon removal; the" rubber disk A mixture of 2.5 parts of w isj round; to. be blown to the depth dimensions of the confined space, i; e., the. disk of the rubber.

composition. increased from. 166' to 500-. mils (a. three-fold increase. or 311 blow) in thickness. while still maintaining. its. original circular dimensions. A cross section of the. sponge. rubber. so: producedis. f'oundlto. have small, even, well?- spacedi. pjoresi.

III

Etepamtiomogt 5,&-hemamethylenespiroiiydamtOZ'Tt:

NH-Q6 This. preparation is; carriedout in general; as:

described under Example I, Part. A, except, that; ;.g- (0.3 mole): of cycloheptanone (Suberone)... 80;g (0.61mole). of; ammonium carbonate monohydrata. 110 m1s...of; 95%;. ethyl alcohol, 70: mls;v

B; Preparation of 1-aminocycloh-eptanecarliosc ylie'a'cid" NH H2304 H20 NH'n This; preparation is carriedout in general in the; same. fashion as described in Example I, Part.

amethylenespirohydantoin and g. (0.3' mole) of.'

601%" sulfuric acid.- are used and thereflux time under' nitrogen is. 41 hours. Thereis. thus ob.- tainedIOfgrams (64% of theory) of li-aminocycloheptanecarboxylic acid as. glistening, white.

7 platelets.

method'f ANALYSIS Calculatediw CaI-I1502NI C, 61.12%; H,.9.62%

NIEI, 15.712". mum (1.611157%; H, 6.69%; N, 8.68%. 60.86%5. 9.65%; 8.671%.

N;lit, 15'6;.7";.l56.5

. The; acid? has alsobeen. prepared by another see Zelinsky: et" a1, supra.

C; Rreparatiim of the. N-carboanhydride of. 1;-

aminocycloheptanecarboxylic. acid;

m re,

A solution of 3.14 g. (0.02 mole) of l-aminocycloheptanecarboxylic acid in 20 mls. (0.02 mole) of 1.013 N sodium hydroxide is placed in a cylindrical glass reactor and cooled to C. in an ice bath. Phosgene is bubbled into the reaction mixture for 2 minutes at the rate of 0.02 mole per minute (100% excess). A'voluminous precipitate is obtained within 14 seconds and the temperature of the reaction mixture rises to 11 C. The almost solid reaction mixture is extracted with 100 mls. of chloroform which dissolves a large portion of the solid. The chloroform extract is washed with Water, treated with anhydrous calcium sulfate for 30 minutes, and the solvent then removed under reduced pressure. There is thus obtained 0.! gram (19% of theory) of the N-carboanhydride of 1-aminocycloheptanecarboxylic acid melting at 145-146 C. Upon recrystallization from mls. of warm benzene to which-is added 25 mls. of warm petroleum ether, there is obtained after cooling and standing 0.35 g. (10% of theory) of the purified N-carboanhydride of laminocycloheptanecarboxylic acid melting at 146-147 C.

ANALYSIS Calculated for C9I-I13O3N1 C, 59.00%; H, 7.15%;

Found: C, 59.01%; H, 7.15%, N, 7.79%

The chloroformand water-insoluble residues remaining from the chloroform extraction are taken up in 20 mls. of sodium hydroxide, cooled in ice, and phosgene is passed into the resultant solution for 2 minutes at 0.01 mole per minute. Chloroform extraction of the resultant reaction mixture, followed by removal of the chloroform solvent at reduced pressure produced an additional 0.2 g. of the N-carboanhydride of 1- aminocycloheptanecarboxylic acid as white crystals melting at 144-145 C., thus increasing the yield of the N-carboanhydride to of theory.

EXAMPLE IV Fifteen (15) parts of the sodium salt of 1- amino x methylcyclohexanecarboxylic acid (prepared from mixed l-amino-x-methylcyclohexanecarboxylic acid which in turn was prepared from a mixture of methylcyclohexanones) in an open reaction vessel protected from the atmosphere by drying tubes was covered with excess liquid phosgene, while the vessel was being cooled in a solid carbon dioxide/acetone bath. The reaction vessel was then removed to an ice bath and allowed to remain under such conditions overnight. The excess phosgene was removed by distillation; the solid product remaining was triturated with chloroform; the resulting slurry of sodium chloride and choloroform was filtered, and the chloroform removed by distillation of the filtrate, all under anhydrous oxygen-free conditions. There was obtained 5.4 parts (37% of theoretical) of White N- carboanhydride of 1 amino-x-methylcyclohexanecarboxylic acid which sintered at 115-125 C. and melted with foaming at 160- 170 C. A fresh sample immersed in a 170 C. bath melted sharply, decomposed with foaming, and became an opaque white solid in one minute.

The spiro N-carboanhydrides of this invention may be polymerized as shown in the following illustrative examples.

Polymerization of the N-carboanhydride of 1- aminocyclopentanecarboxylic acid One (1) part of the N-carboanhydride of 1- 8 l aminocyclopentanecarboxylic acid is dissolved in eleven parts of anhydrous chlorobenzene and the resulting solution refluxed under anhydrous conditions for 57 hours. At the end of this time, 0.0003 part (0.05 mole per cent based on the N-carboanhydride) of cyclohexylamine is added as a polymerization initiator and the solution refluxed for an additional four days. At the end of this time, there is obtained an insoluble solid polymer of l-aminocyclopentanecarboxylic acid, insoluble in xylene, cresol and chloroform, soluble in concentrated, sulfuric acid and infusible at 350 C., showing no discoloration on a copper block exposed to the atmosphere at this temperature.

Polymerization of the N-carboanhydride of 1- dmz'nocycloheznanecarboxylic acid The N carboanhydride of 1 aminocyclohexanecarboxylic acid is heated under nitrogen in an open, tubular container to 160 C. After two minutes at this temperature, carbon dioxide begins to be evolved from the clear, colorless melt. Within 25 minutes the liquid begins to thicken, and within two hours it becomes opaque and finally solid. The polymeric product thus obtained is a powdery, white solid which is infusible at 400 C. It is soluble in v concentrated sulfuric acid and insoluble in 98% formic acid, saturated calcium chloride/methanol solution, 50% lithium bromide solution, water, saturated calcium chloride/formic acid solution, syrupy phosphoric acid, 4 N sodium hydroxide, and concentrated hydrochloric acid. This solubility behavior indicates it to have a high degree of polymerization.

When the above N-carboanhydride is heated at 146 C. polymer formation is greatly accelerated when 0.2% of tetramethylenediamine is included.

Copolymer from the N-carboanhydrides of alphaaminoz'sobut'yric acid and l-aminocyclohemanecarbomylic acid A mixture of two parts of the N-carboanhydride of alpha-aminoisobutyric acid and one part of the N-carboanhydride of l-aminocyclohexanecarboxylic acid is heated under nitrogen to C. in an open glass or glass-lined vessel. A clear melt is obtained almost at once. Within two minutes vigorous evolution of carbon dioxide sets in; with 25 minutes the liquid becomes so viscous that it begins to foam, and after 3 /2 hours it becomes solid. Heating is continued for a total time of 4 hours. The polymer so obtained is a white, amorphous powder which is infusible and darkens only in spots after one minute at 400 C. It has a nitrogen content of 14.65%, as compared with the calculated value of 14.55%, and inherent viscosity of 0.13 and softens at 200 C., then hardens and becomes infusible finally decomposing at 320 C. This polymer gives a positive biuret test of lavender tint and is soluble in chloral hydrate, chloroform, m-cresol, phenol, and benzyl alcohol. It is swollen by benzene and cyclohexane and is insoluble in tertiary butanol, concentrated hydrochloric acid, 98% formic acid, and water. End-group titrations indicate an amino content of 330x 10 per gram of polymer. This indicates a molecular weight of about 3000 and a degree of polymerization (DP) of 27. Infra-red absorption diagrams show the absence of diketopiperazine-type structures.

dioxide occurs at once in the clear melt. heating for ten minutes at about 150 C., exten- .SiVB foaming sets in; the melt then thickens and Copolymer from the ..N- .oa1:boanhydrides .0 .dl-

beta-phenylalanine and 'i-aminocyclohemnecarbomylic acid Amixture of three parts each of the N=-carlmanhydrides of dl-hetaephenylalanine and l-aminocyclohexanecarboxylic acid is heatedunder nitrogen at 146 C. Vigorous evolution of carbon After within minutes it solidifies. Heating is iterminated after a total time of 80 minutes. The white, powdery polymer obtained is soluble in chloroform, hot benzene, and m-cresol, softens at 160 C. and has an inherent viscosity of 0.09. A

clear, colorless, self-supporting film was ob- "tained by pressing at 240 C. under 5000 p. s. i. pressure.

Copolymer from the N-carboanhydrides of glyc'z'ne and 1 aminocycloheccanecdrboarylic acid.

Two parts of the N-carboanhydride of glycine and one part of the N-carboanhydride of 1- a-minocyclohexanecarboxylic acid are ground together in a mortar and then heated under nitrogen at 121 C. for five hours. The mixture 'sinters at the start but does not melt. The product is insoluble in boiling m-cresol and is in- .fusibleon a copper block, charringat320 C.

Copolymer from the N-carboanhydrzdes of 1- aminomycloheranecarbozrylic acid and alphaaminocycloheazy'lacetic acid A mixture of equal parts of the N-carboanhydrides of 1-aminocyclohexanecarboxylic acid and alpha aminocyclohexylacetic acid is heated under nitrogen at 146 C. Vigorous evolutionof carbon dioxide occurs almost at once in the clear melt (after 1 to 2 minutes heating). After ten to fifteen minutes heating evolution of carbon dioxideceases and the melt becomes solid. Heating is terminated after one hour. The white, powdery polymer obtained is soluble in .m-cresol, softens at 180 C. and exhibits an inherent viscosity of 0.09.

Polymerization of the N-carboan'hyd-r-idc of '1- amz'nocycloheptanecarboxylic acid carbon of the carboanhydride or oxazolidine ring is a spire carbon, i. e., the i-carbon is the one annular member common to two rings. The size of the second ring, i. e., the ring other than the oxazolidine ring, is immaterial, but it will normally have from 5 to 7, and preferably 6,

members since others are rare and difficultly formed. Such ring is .preferablycarbocyclic, but it may be heterocyclic, in which case the hetero :atom's may be oxygemnitrogen, or sulfur; also, it may have substituents such as halogen, alky l, alkoxy, and the like which are non-reactive in the polymer-forming condensation.

In addition to the acid. of the examples'th'ere .may be employed, with formation of .thecorreassumes 10 sponding Necarboanhydrides, 3-aminotetr ahydro'th'iophene I3 c'arboxylic acid, 4 -,amino-"1- methyl-piperi'dine-ewearboxylic acid, ;3-amino tetrahydrOIuran- B-carboxy1ic acid, l-amino-Z- methylcyclobutanecarboxylic acid, 'l-amino-Z- .methylcyclohexanecarboxylic acid, l-amino-B- methYlcylohexanecarboxylic acid, 1- amino l- .lmethylcyclohexanecarboxylic acid, 1 amino- .13,3,5 -.trimethylcyclohexanecarboxylic acid, 1- .aniinocyclopentanecarboxylic acid, .l-aminocy- .cloheptanecarboxylic acid, and ,l-amino-rl-nitrocyclohexanecarboxylic acid.

The N-carboanhydrides of this invention may lbesystematically described as 2,5-diketooxazolidines'having the 4-.carbon of the carboanhydride or .oxazolid'ine ring aspiro carbon, 1'. e., the one common member .of two rings.

.The N-carboanhydrides of this invention exhibit marked superiority in heat stability over the -known .Ne'carboanhydrides of amino acids. .This superiority reduces the difficulty of .isolation and handling, and it enhances their utility as polyamide intermediates since it is carried into the resulting polymers even though higher temperatures maybe required for elimination of .carbondioxide. The N-ca-rboanhydrides of this invention :are {thus useful in the .preparationo'f 'polyamides and ,copolyamides through polymer iza'tion, via carbon .dioxide evolution, with them- ;selves or otherN-narboanhydrides. The N -carboan'hydrides are also useful as bactericidal agents.

The polymers obtained from the N-carboanhydrides of the present invention, including the above-mentioned specific N-carboanhydrides are linear roondensation polyamides characterized by recurring alpha-amino acid units '30 to of which are units wherein the alpha-carbon is a member of a ring preferably of 5 to '7 members and preferably carbocyclic which ring is, apart from said alpha-carbon, external :to the polymer Cchain.

I heseipolymers are prepared optionally in the .presence of an organic solvent, by the condensation polymerization (thermal or initiated by water, .ethanol, :phenols, organic acids, or amino hydrogen-containing amines), with carbon diroxide evolution, of compositions all of the react- .ants of which are amino acid N-carboanhydrides ,and which-containfrom30 to 100%, by weight of the reactants, of one or more alpha-amino acid N-carboanhydrides having .the ii-carbon of the .N-carboanhydride or ox-azolidine ring a spiro :carbon, i. e., the :one common member of two rings. The 'spiro .N-carboanhydride must make up at least 30% of the polymerizable components inorder that the polymer may exhibit in effective .measurethe unique properties of the polymers of this invention.

The preferred procedure is to heat the selected .spiro amino acid ,N-carboanhydrideecontaining composition under oxygen-free conditions, de-

.,sira'bly under an inert gas such as nitrogen or carbon dioxide, in a vessel adapted to permit es- ,cape of carbon dioxide, to that temperature at which .carbon dioxide -is evolved at an appreciable rate. This varies somewhat with different ,compounds but is usually in the neighborhood of 70200 and is generally above the melting point of the spiro amino acid N-carboanhydrides. Heating is continued until carbon dioxideevolution ceases with the temperature maintained at the gas revolution point or slightly, 10-20 0., above it. The time ofthe reaction may be shortened or the temperature necessary may be low- :ered, or both, by the use .of catalysts for the decomposition of the "N-carboanhydrides, such as anodes;

'11 water, ethanol, phenols, organic acids such as adipic, or amino-hydrogen-containing amines such as tetramethylenediamine.

Polymers from the N-carboanhydrides of this invention exhibit marked thermal stability over the previously known amino acid polyamides; thus, they do not decompose at temperatures as high as 350-400" 0. Their solubility in organic solvents varies considerably, ranging from high insolubility when a single N-carboanhydride is employed to fairly wide solubilities as the amount of other amide-forming ingredient is increased, although there are some exceptions to the latter generality. The insoluble types may be used as fillers, delusterants for nylon, and pigment carriers. The soluble types may be used to produce films and artificial fibers. The interpolyamides prepared from N-carboanhydrides of this invention are soluble in one or more of the following: sulfuric acid; hot benzene; chloral hydrate; tetralin; five and six-membered alicyclic ketones liquid below 75 C., e. g. cyclopentanone and cyclohexanone; halogenated hydrocarbons liquid below 75 C., e. g. methylene chloride, chloroform, carbon tetrachloride, ethylene dichloride, allyl iodide, benzyl chloride, and chlorobenzene; and phenols and thiophenols liquid below 75 0., e. g. phenol, chlorophenol, thiophenol, resorcinol monomethylether, and m-cresol.

The term inherent viscosity or man. as used herein is defined by the following equation:

7rel "1nh. C

lrel.

solvent 1 being viscosity. In this specification inherent viscosity data refer to results obtained with the polyamide involved dissolved in m-cresol at a. concentration of 0.5 gram per 100 cc. of solution at 25 C.

The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described for obvious modifications will occur to those skilled in the art.

What is claimed is:

1. An N -carboanhydride of an alpha-amino acid in which carboanhydride the 4-carbon of the oxazolidine ring is a spiro carbon of a five to seven atom ring.

2. An N-carboanhydride of an alpha-amino acid in which carboanhydride the 4-carbon of the oxazolidine ring is a spiro carbon, the second ring being carbocyclic and of 5 to 7 carbons.

3. An N-carboanhydride of an alpha-amino acid in which carboanhydride the ll-carbon of the oxazolidine ring is a spiro carbon, the second ring being a six-membered carbocyclic ring.

4. An N-carboanhydride of an alpha-amino acid in which carboanhydride the 4-carbon of the oxazolidine ring is a spiro carbon, the second ring being a five-membered carbocyclic ring.

5. An N-carboanhydride of an alpha-amino acid in which carboanhydride the 4-carbon of the oxazolidine ring is a spiro carbon, the second ring being a seven-membered carbocyclic ring.

6. An N-carboanhydride of an alpha-amino acid in which carboanhydride the 4-carbon of the oxazolidine ring is a spiro carbon, the second ring being carbocyclic, hydrocarbon, and of.5 to 7 carbons.

7. An N-carboanhydride, containing only carbon, hydrogen, the N-carboanhydride nitrogen, and the three N -carboanhydride oxygens, of an alpha-amino acid in which carboanhydride the it-carbon of the oxazolidine ring is a spiro car bon, the second ring being a five-membered carbocyclic ring.

8. An N-carboanhydride, containing only carbon, hydrogen, the N-carboanhydride nitrogen, and the three N-carboanhydride oxygens, of an alpha-primary amino acid in which carboanhydride the Jr-carbon of the oxazolidine ring is a spiro carbon, the second ring being a five-membered carbocyclic ring.

9. An N-carboanhydride, containing only carbon, hydrogen, the N-carboanhydride nitrogen, and the three N-carboanhydride oxygens, of an alpha-amino acid in which carboanhydride the e-carbon of the oxazolidine ring is a spiro carbon, the second ring being a seven-membered carbocyclic ring.

10. An N-carboanhydride, containing only carbon, hydrogen, the N-carboanhydride nitrogen, and the three N -carboanhydride oxygens, of an alpha-primary amino acid in which carboanhydride the l-carbon of the oxazolidine ring is a spiro carbon, the second ring being a sevenmembered carbocyclic ring.

11. An N-carboanhydride, containing only carbon, hydrogen, the N-carboanhydride nitrogen, and the three N -carboanhydride oxygens, of an alpha-amino acid in which carboanhydride the 4-carbon of the oxazolidine ring is a spiro carbon, the second ring being a six-membered carbocyclic ring.

12. An N-carboanhydride, containing only carbon, hydrogen, the N-carboanhydride nitrogen, and the three N-carboanhydride oxygens, of an alpha-primary amino acid in which carboanhydride the 4-carbon of the oxazolidine rin is a spiro carbon, the second ring being a six-memered carbocyclic ring.

13. An N-carboanhydride, containing only carbon, hydrogen, the N-carboanhydride nitrogen, and the three N-carboanhydride oxygens, of an alpha-amino acid in which carboanhydride the 4- carbon of the oxazolidine ring is a spiro carbon, the second ring being carbocyclic, hydrocarbon, and of 5 to 7 carbons.

14. An N-carboanhydride, containing only carbon, hydrogen, the N-carboanhydride nitrogen, and the three N-carboanhydride oxygens, of an alpha-primary amino acid in which carboanhydride the 4-carbon of the oxazolidine ring is a spiro carbon, the second ring being carbocyclic, hydrocarbon, and of 5 to 7 carbons.

15. The N-carboanhydride of 1aminocyclopentanecarboxylic acid.

16. The N-carboanhydride of l-aminocyclohexanecarboxylic acid.

17. The N-carboanhydride of l-aminocycloheptanecarboxylic acid.

18. The N-carboanhydride of l-aminomethylcyolohexanecarboxylic acid.

ROBERT NEAL MACDONALD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,327,162 Baldwin et a1 Aug. 17, 1943 2,389,662 Fisher et a1 Nov. 27, 1945 Certificate of Correction Patent N 0. 2,560,584 July 17, 1951 ROBERT NEAL MACDONALD It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 8, strike out now abandoned,; line 9, after 1947 and before the period insert now abandoned column 2, line 31, for 50.04% read 54.04%; column 6, line 60, for 6.69% read 9.629% line 74, for that portion of the formula reading +2NaC read +21Va0l and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Oflice Signed and sealed this 2nd day of October, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

1. AN N-CARBONANHYDRIDE OF AN ALPHA-AMINO ACID IN WHICH CARBOANHYDRIDE THE 4-CARBON OF THE OXAZOLIDINE RING IS A SPIRO CARBON OF A FIVE TO SEVEN ATOM RING. 